Recovering metals



Nov. 25, 1930. u. A. GARRl-:D

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/ ATTORNEY Nov. 25, 1930. u. A. GARRED RECOVERING METALS x Filed April 8. 1927 4 Sheets-Sheet 4 l A BY v r ATTORNEY Patented Nov. 25, 1930 UNITED STATES PATENT OFFICE y ULYSSES A. GA'NRED, OF JACKSON HEIGHTS, NEW YORK, ASSIGNOR TO ANAGONDA. COPP-ER MINING COMPANY, A CORPORATION OF MONTANA nEcovERINe METALS Application led April 8, 1927. Serial N'o. 181,979. v

In a previous application No. 97,840, filed y March 27, 1926, I have described a process of recovering metals from slags and other'` materials by forcing through the'material a l '51. mixture of finely divided fuel and air.

The present application is a continuation in part thereof with certain additional feai tures. The accompanying drawings illustrate an embodiment of the invention.

tus and stages of the process;

Fig. 2 is a longitudinal vertical section of the vessel in which the blowing takes place;

Fig. 3 is a partial plan and partial section of the same on the line 3 3 of Fig. 2;

Fig. 4 is a front ,elevation of the same;

Fig. 5 is a side elevation of a portion of the same; y

Fig. 6 is a vertical sectional view through a tuyre and connections;

Fig. 7 is a similar view illustrating a modiication.

In many smelting operations it is common to lose considerable values in the slag. For example, in the operation of lead smelters slags containing considerable amounts of zinc are commonly thrown away; and corresponding losses of tin, lead and other metals are common in smelting copper and like operations. l

The object of the present invention is to provide means whereby the metal may be recovered from such slags and other material.

By the present method, hot slag from the blast furnace is charged into the vessel which I call a converter Or, less advantageously, cold broken slag may be placed in the converter and melted.

Pulverized coal or oil or gas or similar finely ldivided Yfuel is forced, together with a quantity of air, into the converter underneath 'the molten slag. The fuel ignites and the burning fuel and-air. The burning fuel produces enough heat to keep the slag molten in spiteof the cooling effect of the air, and

at the s ame time act-s as an agent to assist in separating out the metals from the slag).

- In the case of zinc, for example, the urning coal volatilizes the zinc (first converting Jratus; as zinc oxide. Other metals may be similarly obtained by volatilization. Fig. 1 is a flow sheet of the various appara- The lead and Zinc or other metals vmust first be reduced from the oxide before they can be eliminated from the slag, and this I effect by using an amount of coal dust greater than that which can be burned by the amount Aof air supplied. The excess of carbon reduces the zinc oxide to metallic zinc, which vaporizes at the temperature in the converter and is thereafter reoxidized. Also the excess of carbon remaining in the gas which passesl olf is oxidized.

A The quantity of fuel and air to be employed depends on the nature of the material, but in all instances it is desirable-to force in enough air to contact thoroughly with` the sla and enough fuel to maintain the slag in unc illed molten condition and to contribute the chemical or reducing action promoting separation of the metal. Thisis lespecially important in recovering zinc, to the recovery of which the invention is particularly applicable.

An example of the process applied to the recovery of lead and zinc oxide fumes from lead blast furnace slag is illustrated in Fig. 1. Three slag furnaces or converters 1 are illustrated. The material for treatment comes in at one side on the line 2 and the waste slag furnaces. In this flue there is further oxidaerated and the gas and fume are at the same timeV considerably cooled. The cooled gas and fume pass out by a line 7 which indicates a iiue of steel for effecting the complete cooling requiredbefore the metal oxides can be recovered. This cooling flue leads by two branches to compartments 8 and 9 of the bag house with dampers 10 and 11 by vwhich the fume can be led to rst one and then the other compartment. The oxides recovered pass from the bag house by the line 12 ;V the gas passes by the line 13 to the stack 14.

The bag house illustrates an improvement which is the invention of Frederick Laist and covered in a separate application pending in his name; by which the fumes are switched from one point to another at different stages of the blowing of 'a charge, eliminating impurities and collecting products which are moe or less rich in the percentage content of lea The passing of the fume through the boiler 6 serves the double purpose of cooling it to apslag furnaces. Water passes from the pumps proximately the degree required and of utilizing the heat of vaporization and the heat Vof j(fzlombustion of the metals and fuel within the The boiler may be used for various purposes. I have illustrated it as supplying steam through a line 15 to an air compressor and water pumping plant 16. The com` pressed air passes through the line 17 to the through the line 18v to the slag furnaces for water cooling various parts as described hereinafter.

The hot water over'owing from the cooling jackets passes out by the line 19 and the feed water hne 2O to the boiler and by the line 21 tothe cooling tower 22 where it is cooled suiiciently to be passed through the line 23 Vto the pumping plant.

Assuming pulverized coal to be used as l fuel, the pulverizing plant'24 is used to supply coal along the line 25 to the slag furnaces and along the line 26 to the blast furnaces.

The'invention may be applied to various materials containing metal oxides such, for example, as cold slag taken from a dump or bin as previously explained, or it may be apl plied to slag coming directly molten from blast furnaces.

In Fig. 1, three dierent materials are4 shown. The line 27 indicates the introduction of any such material containing zinc, assuming this to'be the metal we are seeking to' recover. The line 28 indicates slag coming from the set of lead blast furnaces 29. The lead slag from the dump 30 may be carried directly to the slag furnaces. But there are certain advantages in carrying it to the blast furnaces as indicated by way of the line 31.

In the blast furnaces it is mixed with the usual charge of lead ore. A twdfold ad vantage results from this step, and is beneficial to the operation of the blast furnaces,

i iirst in increasing. the total-tonnage treated content than that w ich would be produced from the dump through the blast furnaces in this way there is probably an economy in the actual cost of melting compared with the'separate melting of the dump slag alone.

The preferred form of converter is shown in Figs. 2 to 6. The hearth is made of a layer of silica 32 with a superposed layer of magnesite brick 33. The sides 34, ends 35 and 36 and roof 37 and vuptake 38 are made of hollow steel sections through which water is circulated to keep them cool and to resist the corrosive action of the molten charge. VThe up-take from each converter is covered by an arch 39 of brick-work which is extended to form part of the common flue 40 (Fig. 4). The up-take 38 extends across the full width of the converter about halfway between the front and the back.

At the rear of the roof there is an opening 40 above which is a hopper 41 through which the molten charge is introduced from ladles, after which the opening is closed by a damper 42. At the -front side Yof the 11p-take 38 there are openings 43 (Fig. 4) to admit airfor oxidizing the escaping gas and fuels. In the front wall there are tapping ports 44 made in water cooled cast blocks 45.

The barren slag after a blow will be tapped and run off into chutes 46 Afor any convenient disposal. Also in the front wall there is a pee -hole ordinarily covered by a slide 47 of re-brick.

The introduction of air and fuel is at numerous points along the lower parts of the two side walls 34. For this purpose two degrees of air pressure are preferred and the wall (Fig. 6). Each tuyre at its outer end is continued ina fitting 54 having lateral conn-ections to a branch 55 from the high pressure pipe and to a branch 56 from the low pressure pipe and also to a branch 57 constituting a slag pocket normally protected by a fuse-58 which will burn out and permit the escape of any molten slag which backs up into the tuyre. At its outer end the fitting 54 has apunch rod opening closed by a plate 59 which is pivoted to permit swinging inward but not outward so that the pressure of air will hold it closed.

Fig. 7 illustrates in vertical section a-fragment of an ordinary tilting converter with a rounded bottom. The shell 60 is stifened bv vertical braces 61 and lined with magnesite brick or. similar refractory material 62 i through which the tuyres 63 extend, termi? nating at its inner face. At the outside there' is a main 64 carryin air at low pressure and communicating by pipe 65 with a fitting 66 on the outer end of the tuyre which has a check` valve 67 closing a hole 68 through which a poker or clearing bar can be introduced in case the tuyre is choked at -its inner end.

This is similar to the opening and valve 59 of Fig. 6. The pipe 69 carries the high presj owdered coal which pass there sureair and from throug a branch pipe 70 to the tuyre,

It has been previously proposed to blow coal dust throu h a bath of slag with an yain current, butwit out pointing out the proportions and without sufficient infomation in detail to enable one to carry out the process successfully. I have ascertained by considerable experimentation on a practical scale that forpractical success it is necessary to carry out the process under the conditions herein described and hereinafter' claimed.

Variousother modifications of the process and apparatus may bemade by those skilled in the art without departing from 'the inventionas delined in the following claims.

What I claim is 1. In the recovering of volatile metals from slag and the like, the method which consists in lforcing through the' molten slag y .finely divided fueland air, introducin the fuel With-air under high pressure an introducing air se arately under low pressure and collecting t e resulting fume.

2. In the recovering of volatile metals from blast-furnace slags, the method which consists in adding cold slag to the chargel of the blast furnace, carrying the molten slag from the blast furnace to a slag furnace, Y forcing through such molten slag finely divided fuel and air and collecting thefxfume.

3. In the recovering of volatile metals from blast furnace slags, the method which consists inv adding cold slag tothe charge of the blast furnace, carrying` the molten slag from the blast furnace to a'slag furnace, adding to the charge in the slag furnace cold ma-l terial containing the'metal to be recovered and forcing through the charge in the.slag furnace nely divided fuel and air sufficient to maintain the charge molten and collecting the fume.- l l In witness whereof, I have hereunto signed my name.

ULYssEls A, GARRED. 

